With the help of a search engine like Google, the Internet has become a major venue for people to receive information. But finding and serving information best matching a particular individual's needs and search interests has been an ongoing challenge for a search engine. First, different individuals have quite different preferences for information and it is not easy to accurately identify an individual's search interests. This issue is further complicated by the fact that a person's interests are often dynamic and vary over time. Second, many web pages on the Internet are either unclassified or misclassified. Without the classification data necessary for profiling the information provided by web pages, a search engine's quality of service may be adversely affected for including less relevant web pages in the search results while missing more relevant ones.